The present invention relates to a spinal transpedicle drill jig, and more particularly to such a drill jig adapted for providing a passage for a transpedicle screw to pass through so as to provide a safer and easier way during operation.
Heretofore, fractures or dislocation of spine were often treated by utilizing Harrington Hooks on the lamina or Luque Sublaminal Wiring to remedy vertebral bodies. However, in this way, it was necessary to fit at least five vertebral bodies, so as to easily cause some side-effects such as backache and the like.
Thus, those skilled in this art have found that to fix the vertebral bodies by means of transpedicle screws reduces the precentage of side-effects occurring. It has been proved from biomechanical study that fixing vertebral bodies by transpedicle screws provides greater stability than conventional hooking and wiring. Broadly speaking, the more deeply the screws are drilled in the pedicle, the more stable the vertebral bodies will be fixed. However, the location of drilling and the angle between the central axis of the vertebral bodies and the direction of drilling play important roles. Slight deviations of drilling direction could injure the nerve roots or spinal cord. Therefore, methods to prevent nerve roots and spinal cords from being hurt and to stabilize using transpedicle screws to fix the vertebral bodies are important factors in clinical operation.
A number of dissections on thoracic spine and lumbar spine, the fact of that the crossing point of the line along the lateral border of the superior articular process and the line along the center of the transverse process is the preferred location for drilling has been established. Also, the preferable angle measured from the thoracic spine between the axis of the transpedicle and the axis of the vertebral bodies has been statistically determined to be 10 degrees and the angle measured from lumbar spine is preferably 15 degrees, as analyzed on the transverse plane.